The present invention relates in general to a relay control circuit for controlling a relay and, in particular, a relay control circuit for controlling a light fixture circuit.
In the prior art, HID lamps are operated between a high or full intensity light level and a dim or reduced light intensity level in response to a control signal. The change of intensity level of the light output of the HID lamp is effected by changing a capacitance value in the light fixture circuit. This is accomplished by connecting and disconnecting a first capacitor across a second capacitor by means of relay contacts. Although the prior art systems provided good operation for switching the HID lamp between high and low light output settings, it has been found that when the relay has normally-closed contacts, the useful life of the relay is limited. The drawback of such a controller circuit is in the deactivation of the relay. The prior art controller circuit that controls operation of the relay produces a gradually decreasing current flow through the coil of the relay. As a result, the speed with which the rocker of the relay opens is slower than if the current were suddenly switched to zero through the coil. This places less force on closing the normally-closed contacts than is desirable. This lower contact force causes the contacts to degrade more rapidly, eventually failing by welding together.
The present invention overcomes these drawbacks in the prior art controller.